They ran him up to five Gs. That wasn’t so bad; he ought to be able to withstand as much as fifteen Gs. But it was enough to keep his chest pressed against his backbone, and he felt he had to force his rib cage open just to take a breath.

Stopping, he found out, was the worst part. When he slowed the sideways forces started to kick in, Coriolis forces, and he felt as if he was tumbling, and threw up heavily before they could haul him out of the cage, his vomit probably laced with barium.

To familiarize him with the Space Station, now being used as an orbital construction shack for the Moon spacecraft, he was taken to the Sonny Carter Neutral Buoyancy Laboratory. This was located up near Ellington Field.

The weather that day was clear after some days of cloud, and the sky was streaked by toy-like T-38s, astronauts anxiously keeping up their flying hours. Henry suffered a corny NASA moment, when he found himself at the entrance plaza of the facility looking up at a slab of blue July sky framed by a Stars and Stripes, while a T-38 flew past a milky Moon.

But Venus was already rising, a malevolent smear of light.

The Carter facility turned out to be a gigantic rectangular pool, all of forty feet deep. Henry was kitted up in a bulky, multi-layered pressure suit, with a heavy backpack to keep him alive. Inside his bubble helmet, enclosed, he could smell lint and metal and the hiss of air; his own breathing was noisy.

He was lowered into the pool on a frame elevator. Divers took his arms and helped him into the water. The colour of the water was a deep blue — just because of its depth, not because of any additives — and it was so deep the divers who accompanied the astronauts on their dives had to undergo decompression procedures. The astronauts, in their pressure suits, were pretty much immune to pressure changes.

He could feel the resistance of the water, see its bluish haze extending around him, but in his bubble of air he was as dry as desert dust, cut off. Beside the graceful, seal-like divers, he felt clumsy, stiff, barely able to move. He wondered if he would feel so isolated in space.

The pool was full of gigantic toy-like trainers: an open Shuttle payload bay so he could practise hand-cranking the big doors closed, and huge pieces of Station, through which he swam.

Sonny Carter, it seemed, was an astronaut who had died in a plane crash. This facility seemed like a good memorial to Henry. The pool afforded him moments of peace, of slowness and relative control, little oases in the chaos that had overtaken his life.